In logging while drilling and drilling operations, near-bit measurement can obtain position information of a drill bit in real time, thereby characterizing real-time drilling trajectory information, so that a ground operating engineer can adjust a drilling speed and a drilling direction in real time and complete a drilling operation according to the set borehole trajectory. A sensor of the near-bit measurement is installed between the drill bit and a mud motor. Due to a special structure (which is completely a mechanical mechanism without electrical connections such as stringing, unless a structure of the screw is modified) of the mud motor, a near-bit measurement unit is not electrically connected with a MWD system. Accordingly, measured data of a near-bit measurement stub may be transmitted to the MWD system above the mud motor in real time only through a wireless manner, and then transmitted to the ground through a mud pulse telemetry system.
The wireless short-transmission system uses an electric field formed by the emitter and the receiver to realize a wireless short-transmission function. An insulator is inserted between a positive pole and a negative pole of the emitter to achieve electrical isolation between the two parts of the emitter. The receiver is installed at about 10 meters from the emitter on the other side of the mud motor, and an insulator is also inserted between a positive pole and a negative pole of the receiver to achieve electrical isolation between the two parts of the receiver. After an electrical signal emitted by the positive pole of the emitter passes through a stratum and a wellbore mud channel, a potential difference exists between the positive pole and the negative pole of the receiver, and then returned to the negative pole of the emitter through a loop formed by the mud motor. Due to a difference in resistivity values of a stratum environment and mud, the dynamic range of the potential difference formed between the positive pole and the negative pole of the receiver is very large. In a research and development process, there is a need for calibrating a transmitting power and a receiving gain for a case of resistivity values of different drilling strata in combination with the environment. However, wireless short transmission achieves wireless signal transmission by means of a closed-loop electric field under a wellbore mud environment. Since the wellbore environment at a well site is tough, an experimental operation in the actual well site is inconvenient, time-consuming and costly so that research and development costs are high, resulting in incapability of realizing testing of the system under different drilling environments and great difficulty in research and development.